In the 1 000 kV UHV AC transmission line from Huainan to Shanghai, the average weight and height of double-circuit steel tube tower are 200 t and 120 m. The monitoring system was developed to improve the safety and reliability of assembling tower with inside suspension pole, which could monitor the forces and angles for inside suspension pole system, and limit the data in the allowed scope to eliminate the hidden trouble of safety in the construction process of steel tube towers.